The investigators examine whether adding yoga-based therapy (YBT) to treatment as usual (TAU) for young adult women (age 18-34 years) with a primary diagnosis of MDD leads to (1) greater reductions in symptoms and (2) greater cost-effectiveness in that the economic benefits of adding YBT to TAU outweigh the costs.

BACKGROUND Major Depressive Disorder (MDD) is widespread, as nearly one in five Dutch will experience the disorder within their lifetime. In addition to individual suffering, MDD creates great economic costs in the Netherlands and is a leading contributor to the national disease burden. Although first-step interventions can be helpful, many individuals with MDD do not seek treatment and current interventions often fail to prevent the development of chronic, relapsing MDD. There is thus a pressing need to develop and test new interventions for depression. This need is particularly urgent in young adult women, as this population is especially vulnerable to developing MDD. Yoga-based interventions represent an innovative approach with great potential for treating depression. The rationale of using yoga as a MDD intervention in young women includes initial findings that yoga reduces depressive affect and yoga's appeal in this population. Although the initial findings are promising, previous research has a number of methodological limitations such as insufficient statistical power, and short follow-up periods. The proposed project is designed to use rigorous methods to examine yoga as a treatment for acute depression and as means of preventing the transition to a chronic, relapsing disorder in a sample of young women.

OBJECTIVE The overall objective of this project is to examine the potential benefits of adding a yoga-based intervention (YBI) to treatment as usual (TAU) for young women with major depressive disorder (MDD). This objective will be examined with the following four specific aims: (1) to examine whether adding YBI to TAU leads to greater and sustained reductions in symptoms, and (2) better general functioning in young women with MDD at post-intervention and at 6- and 12-month follow-up, (3) to examine the cost-effectiveness of adding YBI to TAU and, (4) these effects are mediated by change in rumination, self-criticism, intolerance of uncertainty, interoceptive awareness, and dispositional mindfulness.

HYPOTHESES The hypotheses (H) are that compared to TAU, YBI+TAU will lead to: (H1) greater reductions in depressive symptoms, assessed with clinician-administered and self-report measures, and (H2) better general functioning, defined as (H2.1) daily functioning, (H2.2) quality of life and physical health, and (H2.3) positive psychological functioning. The investigators further hypothesize that (H4) compared both to TAU, YBT (+TAU) will show greater cost-effectiveness, and that these YBI effects on symptoms of depression are partially mediated by (H4.1) reduced self-report and implicit rumination about the causes and consequences of negative events and moods, (H4.2) reduced self-report and implicit self-criticism/increased self-compassion after perceived failures, (H4.3) decreased intolerance of uncertainty, (H4.4) increased body awareness/interoceptive awareness, and (H4.5) increased mindfulness.

STUDY DESIGN The study will consist of a randomized controlled trial comparing YBT+TAU with TAU. Assessments are completed at pre- and post-intervention (or equivalent time period in TAU), and at 6- and 12-month follow-up.

STUDY POPULATION Young adult women (age 18-34 years) with a primary diagnosis of MDD.

INTERVENTION The intervention will consist of manualized YBT administered in 9 weekly 90-minute group sessions with home practice +TAU.

USUAL CARE TAU will consist of interventions recommended by the Dutch guidelines for depression, including psychotherapy, pharmacotherapy, psychosocial support by psychiatric nurses, or some combination of these.

OUTCOME MEASURES Primary outcome measures will consist of clinician-administered and self-report measures of depression symptoms and the presence/absence of a diagnoses of Major Depressive Disorder. Secondary outcome measures are daily functioning, quality of life and physical health, and positive psychological functioning. Potential mediators are self-report measures of perseverative thinking, self-criticism, intolerance of uncertainty, interoceptive awareness and dispositional mindfulness, and implicit measures of perseverative thinking and self-criticism. Quality-Adjusted Life Years will be used as primary outcome measure in the economic analysis.

SAMPLE SIZE/DATA ANALYSIS A sample of N=64/group will be recruited in order to have power of 80% (alpha=.05) to detect medium effect size differences between groups. Allowing attrition of 25%, 170 (85/group) patients will be recruited. Repeated-measures ANOVAs and Chi-square analyses will be conducted.

COST EFFECTIVENESS ANALYSIS An economic evaluation will be conducted alongside the clinical study to assess the potential cost-effectiveness of YBT compared to TAU from a societal perspective. A budget impact analysis (BIA) will be conducted to inform decision-makers about the potential financial consequences of the adoption and diffusion of YBT in the Dutch healthcare system.

Inclusion Criteria:

• Primary diagnosis of a major depressive disorder.
• Age ≥ 18 and ≤ 34.
• Ability to fluently read, write, and speak Dutch.

Exclusion Criteria:

• Current diagnoses of bipolar disorder and substance dependence.
• Current psychotic symptoms.
• Active suicidality.
• Unwilling or inability to attend to 9 weekly sessions of yoga.
• Regular yoga practice (on average over the past 6 months, 30 or more minutes per week).

The project uses a blinded rater to assess the primary outcome measure of symptoms of depression